The present invention relates to hydraulic propulsion apparatus and more particularly to improvements in hydraulic jet propulsion systems for watercraft.
Hydraulic jet propulsion systems of the type to which the present invention is directed generally comprise a water conduit arrangement disposed at the rear of the watercraft to be propelled, which conduit consists of an intake section, a pump section, and a discharge section. Surrounding water from under the craft is drawn into an intake passage provided with a flow filtering screen in the intake section and passes to the pump section. The energy of the water incoming to the pump section, from the intake section, is increased by a pump assembly during flow through the pump section so that water with increased energy leaves the pump section and flows into a discharge chamber passage in the discharge section. In the discharge chamber passage there occurs an increase in the speed of water flow due to the drop of its static pressure, to a level about equalling the atmospheric pressure above the surrounding water surface at the cylindrical exit of the chamber. At the cylindrical end of the discharge chamber passage, the water is ordered into an organized flow. Upon leaving the end of the discharge chamber passage, the water in the form of an organized jet exerts a force on the propulsion system equalling the mass of discharging water, times the difference of its speed in relation to the speed of the craft equipped with the system minus the speed of said craft in relation to the surrounding water.
In order to steer the craft, there are attached control means to the propulsion system consisting of direction and reversing means.
The pump assembly, which increases the energy of water flow, is driven by a prime mover, usually an engine within the craft or of the outboard type, which is connected to the pump assembly, by a drive shaft directly or by a drive transmission.
In the past the various sections of the propulsion system have involved structural arrangements with complicated, heavy and expensive parts requiring constant & time-consuming maintenance and resulting in limited overall efficiency. Propulsion systems of the hydraulic jet type, consequently have found little application in smaller watercraft using power plants of under 100 HP output.
The present invention embodies several improvements and simplifications in construction which provide an hydraulic jet propulsion system whose total efficiency attains and even exceeds that of conventional propulsion systems such as Outboard (O/B), Inboard-Outboard (I/O) and Inboard (I/B).
Also, the static thrust of the present hydraulic jet propulsion system and its thrust in the low speed range which is necessary to permit rapid craft movements in conditions of sliding, is at least 15% higher than the same thrust of the said conventional propulsion systems installed in the same craft (i.e., boats of the same shapes and weights), using the same power engine, with equivalent maximum speeds.
Accordingly, the present invention involves the application of new construction means to hydraulic jet propulsion systems that results in a system of minimal dimensions (gabarit) and decidedly less weight than currently manufactured jet propulsion systems. It further results in a propulsion system of greater simplicity, greater reliability in functioning, and lower production costs.
In addition, this invention permits proper location of the propulsion system in the hull of the boat, so that the space taken up by the system and its prime mover is small; and the assembly and disassembly of the main sections of the system takes less than twenty minutes.